There are five primary categories of taste that are sensed by humans: sour, salty, sweet, bitter and umami (savory or the taste of glutamate). The taste of a substance is sensed by taste receptor cells located in taste buds primarily on the surface of the tongue and palate in the oral cavity. Each of the primary taste qualities is sensed by a specific mechanism. It is believed that sour and salty tastes are detected by the passage of ions, hydrogen and sodium respectively, through the ion channels in taste bud cells. This triggers a nerve impulse that is sensed in the brain as sour or salty. In contrast, it is believed that sweet, bitter and umami tastes are perceived by physical binding to receptors. In general, sweet, bitter and umami sensing taste cells have G-protein coupled receptors (GPCRs) on their surface. These receptors are activated when they bind to tastants, which initiates a series of signaling events that trigger a nerve impulse that is sensed in the brain as sweet, bitter or savory.
Over the past several years, there have been a number of advances in research on taste perception. New taste receptor proteins have been identified in mammals, particularly two families of G-protein coupled receptors (T2Rs and T1Rs), which are believed to be involved in taste perception. Such receptors are discussed in more detail in International Publication Nos. WO 02/064631 and WO 03/001876. These publications disclose that co-expression of certain T1R receptors results in savory or sweet taste receptors that respond to savory or sweet taste stimuli, respectively.
Recent advances in the understanding of taste perception have created interest in identifying new compounds for stimulating these taste receptors. In particular, research efforts also have been directed to methods of identifying compounds that may enhance the primary taste perceptions, such as sweet or savory perceptions. The development of substances that provide flavor enhancement is of particular interest, and such substances are generally referred to as taste or flavor enhancers, or potentiators. These substances have been thought to contribute taste, aroma and feeling factors, as well as potentiate and suppress other flavors. The activity of taste or flavor enhancers is often referred to as synergistic because they enhance or increase the perception of another substance.
One category of taste potentiators of particular interest are compounds that enhance sweetness. Although naturally occurring carbohydrate sweeteners, such as sucrose, are the most widely used sweeteners, they suffer from the disadvantages of high cost and high caloric content. Artificial sweeteners have been designed that overcome these problems but they are sometimes rejected by the consumer for not having a sufficiently “sucrose-like” taste. Artificial sweeteners have different sweetness profiles from that of sucrose and often suffer from side effects such as delays in the onset of sweetness perception and/or unpleasant aftertastes.
Compounds are known which, when combined with a sweetener, modify the taste of the sweetener. Such compounds are usually referred to as sweetness modifiers or potentiators. They may act to enhance or inhibit the perception of the sweetness of the sweetener or may affect the sweetness profile in some way. For example, Canadian Patent No. 1208966 discloses a broad range of aromatic compounds which are claimed as sweetness modifiers.
European Patent No. 0132444 and U.S. Pat. No. 4,627,987 describe 3-hydroxybenzoic acid (3-HB) as a sweetness potentiator and exemplify its use with sucrose, aspartame and saccharin to enhance sweetness when employed at pH 2.0 to 5.5.
2,4-Dihydroxybenzoic acid (2,4-DHB) also is described as a sweetness potentiator, but the literature is ambiguous as to its effects. In U.S. Pat. No. 5,232,735 it is listed as a “substantially tasteless sweetness inhibitor” whereas in Canadian Patent No. 1208966 the addition of 0.2% 2,4-DHB to a 5% sucrose solution is said to have resulted in an increase in sweetness. International Publication No. WO99/15032 describes the use of 2,4-DHB with aspartame to increase sweetness synergistically and provide a more “sucrose-like” taste and mouthfeel. The combination is considered peculiar, in that the same effect is not observed when 2,4-DHB is combined with the alternative artificial sweeteners, alitame, Ace-K (acesulfame potassium), saccharin or even a mixture of aspartame and Ace-K. U.S. Pat. No. 6,461,658 claims that 2,4-DHB improves the sweetness delivery profile of the artificial sweetener sucralose by significantly reducing the length of time during which sucralose sweetness is perceived. The same effect is not observed for aspartame even though this might be expected in light of International Publication No. WO99/15032. FIGS. 1 and 2 and Tables 1 and 2 of U.S. Pat. No. 6,461,658 seem to indicate that 2,4-DHB has a slightly inhibitory effect on the sweetness intensity of both sucralose and aspartame although this is not discussed in the text.
International Publication No. WO00/69282 describes the modification of the taste and physicochemical properties of the sweetener neotame by the addition of at least one taste modifying hydrophobic acid additive. The taste modifying hydrophobic acid additive is limited only in that it must positively affect at least one taste characteristic imparted by neotame. These characteristics appear to be related to the sweetness profile, specifically the onset and linger period, but the examples do not describe how the characteristics have been affected. 3-HB and 2,4-DHB are listed among a very large number of such additives.
Additionally, there have been a number of recent developments related to methods of identifying substances that function as taste potentiators. Various assays have been developed to identify target compounds that modulate the activity of taste receptors, and thus, may become successful taste potentiators. For example, International Publication Nos. WO 02/064631 and WO 03/001876, referred to above, disclose assays and high-throughput screens that measure certain T1R receptor activity in the presence of target compounds.
U.S. Pat. No. 6,955,887 to Adler et al. discloses methods for identifying taste potentiators using newly identified mammalian taste-cell-specific G-protein coupled receptors. More specifically, U.S. Pat. No. 6,955,887 teaches methods for screening target compounds that may be used to modulate the sweet taste perception.
Various other methods for screening compounds that may be used as taste potentiators are disclosed in the U.S. Patent Publication Nos. 2005/0287517A1, 2005/0084932A1, 2005/0069944A1, 2005/0032158A1, 2004/0229239A1, 2004/0209286A1, 2004/0191805A1, 2004/0185469A1, 2004/0175793A1, 2004/0175792A1, 2004/0171042A1, 2004/0132075A1, 2004/0072254A1, 2003/0232407A1, 2003/0170608A1 and 2003/0054448A1.
Despite progress in developing methods for identifying new taste potentiators, there is still a need for beverages that include such taste potentiators, particularly sweetener potentiators. It would be desirable to develop a sweetener potentiator composition that allows the quantity of natural or artificial sweetener in a beverage product to be reduced, thereby reducing the cost of production and the calorie content of the beverage product, but which avoids adverse effects on flavor.